There is little difference between the two. In fact, the tenderloin is just one muscle from the regular loin.
The pork loin consists of a series of thick muscles which go along the back of a pig and it is usually marketed as a â€œloin roastâ€ in most grocery stores. The tenderloin is going to be the loin roast which has two parts with one part that is round and slightly dark than the other.
The tenderloin consists of one specific muscle from the very end of the loin itself; it is significantly thinner than the loin roast so it typically cooks a lot faster.